Field of Invention
This invention relates to a structure applicable to integrated circuits, and particularly relates to a contact pad structure for electrical connections of multiple levels of conductors.
Description of Related Art
In a three-dimensional (3D) device array, such as a 3D memory, the conductive lines of the respective levels of devices need electrical connection, so the conductive layers of the respective levels have to be exposed in a contact area for later electrical connection. As a result, a staircase contact pad structure is formed.
In order to form a staircase contact pad structure for N levels of devices, conventionally, N-1 photomasks are used to perform N-1 lithography and etching processes to remove different numbers of levels of conductive layers from N-1 regions in the contact area. However, such method is quite tedious and needs accurate process control for the tight pitch, so the manufacture cost and the process difficulty are increased.